Self-locking screw



Oct. 24, 1939. W. A PURTELL 2,177,003

I SELF-LOCKING SCREW Filed Oct. 9, 1937 /NvE/vTaR APU/fell.

A rron/vfzx Patented oei. 24, 1939 UNITED STATES PATENT OFFICE 2,177,003 SELF-LOCKING SCREW William A. Purtell, West Hartford, Conn.

Application october 9, issa'serial No.

6Claims.

My invention relates to self-locking screws.

It has among its objects to provide an improved screw having improved means in its threads to act against loosening of the screw after it has been entered in a companion tapped member, while permitting .ready insertion of the screw. A further object of my invention is to provide an improved portion on the threads of screws whereby the screws are prevented from working 0 loose, as by vibration or other uncontrolled stresses. Another object is to provide an improved self-locking screw having one or more turnsr of its thread shaped in an improved wave-` like form to bind against the standard edges of the thread of a companion member, the wavy edge on the thr'ead being formed at little or no addi-tional Acost 4over the expense of producing standardthreads. These and other objects, together with other advantages of my improved 80 construction, will hereinafter more fully appear.

In the accompanying. drawing, I have shown for purposes of illustration certain forms which my invention may assume in practice.

In the drawing:

Figure 1 is a side view of a set screw embodying the features of my invention, the screw being shown partly inserted in a companion member, illustrated in section;

Fig. 2 is an enlarged axial sectional view of a part oi the screw and companion member taken on the line 2 2 of Figure 1 but vshowing the screw fully inserted in the companion member;

Fig. 3 is a similar view on the line 2 2, the companion member being omitted;

Fig. 4 is a View similar to Figure 3, showing an alternative form of locking screw, and

Fig. 5 isa straight line projection of the edge I of the thread in either form of locking screw.

Reference is rst made to Figure 1, in which I have shown a socketed set screw l, having a.`ny standard or suitable thread 2 thereon and being entered in a tapped companion member 3, a part of the thread 2 being formed in an improved manner, as indicated at l, to produce my improved locking means.

Herein, my improved locking means is provided preferably in the second turn of the thread 2 from the outer end of the screw, although it will be understood that any other desired turn of the thread; or that more than'one turn ofthe thread, maylbe so provided. The locking means comprisesfas shown in Figures 1, 2 and 3, a turn of the thread in which the standard thread angle has been reduced and in which the face oi' the thread is concave in prole and tapered outwardly to a thin edge or crest 5, the thin edge being made wavy or ruined in contour so that it will appear when projected, as in Figure 5, as a typical plotted curve of points from the crest of the adjoining turns of thread.

As a, result, diierent Waves of the several component wavy turn of thread increases the inherent resiliency or spring in the steel and gives a very 25 satisfactory binding effect.

If desired, the locking turn 4 of the thread 2 When a screw provided with my improved 45 locking means in either form, is entered into a suiiicient to prevent looseningby vibration or other jarring actions Vand the screw remains irmly seated in the tapped opening until removed f 2 by manual means. Attention is here directed to the possibility o f providing s'et screws, cap screws and other threaded fastening members with my improved locking means at little or no additional cost, while increasing the utility and effectiveness of these members. It will also be evident that thescrew may be oi the self-tapping` type.

i. e. wherein the first threads thereof form corresponding threads in a companionv member. These and other advantages of my improved construction will, however, be clearly apparent to those skilled in the art.

While I have in this application speciiically shown certain embodiments which my invention may assume in practice, it will be understood that the same are shown for purposes o! illustration and that the same may be modified and embodied in other forms without departing from its spirit or the scope of the appended claims.

What I claim as new and desire 'to secure by LettersPatent is:

1. In a locking screw, means on the thread of the screw to grip the thread of a companion membe comprising a series of reverse waves in the crest'on a portion of the thread and a normal root for said portion.

2,-In a locking screw, means on the thread to cause binding with the thread of a companion member, said means comprising a portion of thread having a base free fron'i' off-sets in prole and a crest deformed alternately in direction to touch alternately the strongerroot portion of the following and preceding turns of thread of the companion member and to bind against the same.

. 3. In a locking screw, means on the thread to cause locking with the cooperating thread of a previously untapped companion member, said means comprising a resiliently tempered thread portion having a base 'iree from oil-sets crest is in the form in `proille and on which the of a wave providing contact without deformation of the side of the stronger root portion of said cooperating thread in the companion member.. v

4. Inja locking screw, means on the thread to cause locking with the cooperating thread of a companion member, said means comprising a resiliently tempered thread portion having a base free from oil-sets in prole and on which the crest has a plurality oi oppositely directed waves providing contact with the opposite sides of the stronger lroot portion of turns of said cooperatling thread in the companion member adjacent said waves and without deformation of said root portion,

5. In a locking scre means on the thread to cause locking wththe cooperating thread ci a companion member, said means comprising a thread portion in which the face ofthe thread is concave in (prole, and on which the crest is in the form of a wave providing contact with the side of the cooperating thread in the companion member.

6. In a locking screw, means yon the thread to cause locking withv the normal thread ,of a companion member, said means comprising-a thread portion having a base free from off-sets inl prole in which the thread size'is the same as that of the other turns and on which the crest is in the form of a waveproviding bindingcontact without deformation of the side of the stronger root portion oi said cooperating normal thread in the companion member.

A. PURTELL. 

